1. Field of the Art
The present invention relates to a method of cleaning and disinfecting a contact lens by using an iodine-associated or iodine-complex polymer as an iodine germicide or disinfectant. In particular, the invention is concerned with such a method which permits effective cleaning and disinfection of the contact lens while assuring a high degree of safety of the eyes of the user.
2. Discussion of the Related Art
Generally, contact lenses are classified into non-water-absorbable or non-water-content contact lenses and water-absorbable or water-content contact lenses, or hard contact lenses and soft contact lenses. These contact lenses may be soiled with deposits such as protein lipid during wearing of the contact lenses on the eyes, which deposits derive from tear and lipid of the eyes. These deposits adhering to the contact lenses deteriorate the wearing comfort of the contact lenses as felt by the lens wearer, lower the eye sight of the lens wearer, and cause various troubles with the eyes such as hyperemia of the conjunctiva. In view of those problems, it is required to regularly clean the contact lenses by using a cleaning agent which contains a surface active agent and a protease, for instance, so as to remove the deposits for safe and comfortable wearing of the contact lenses.
When the contact lenses are continuously worn on the eyes, bacteria tend to adhere to and proliferate on the surfaces of the contact lenses, especially the surfaces of the water-content contact lenses. In view of this, it is required to disinfect the contact lenses every day for preventing the eyes of the lens wearer from being infected with the bacteria. Although the non-water-content contact lenses are not necessarily required to be disinfected as frequently as the water-content contact lenses, the non-water-content contact lenses are stored in a storing liquid which contains a germicide, so as to prevent proliferation of microorganisms during storage of the contact lenses which have been removed from the eyes.
Generally, the contact lens is cleaned and disinfected in different steps. However, it would be more convenient to the contact lens user if the contact lens can be cleaned and disinfected simultaneously in a single step. In view of this, there are proposed various methods of simultaneously cleaning and disinfecting the contact lens.
For disinfecting the contact lens, there have been practiced a thermal disinfecting method in which the contact lens is heated for disinfection by using a suitable apparatus for boiling the contact lens, and a chemical disinfecting method in which the contact lens is disinfected by a chemical disinfectant. As one example of the chemical disinfecting method, a technique which uses an iodine disinfectant or germicide has been attracting a great attention. The iodine disinfectant or germicide exhibits excellent antimicrobial activity and safety to the eyes of the user. The method using the iodine disinfectant or germicide, however, suffers from various drawbacks which result from the use of the iodine as described below. Accordingly, the iodine disinfectant or germicide is not capable of exhibiting its excellent disinfecting effect to a maximum extent while cleaning the contact lens.
For disinfecting the contact lens, the chemical disinfecting method is recently employed more often than the thermal disinfecting method since the chemical disinfecting method does not use the boiling apparatus as required in the thermal disinfecting method, and assures a simplified disinfecting procedure, so that the contact lens is disinfected at a relatively low cost. In the above-described chemical disinfecting method which uses the iodine disinfectant, the iodine is easily uptaked in the contact lens, whereby the contact lens is colored in amber or reddish purple peculiar to the color of the iodine after a relatively long period of contact of the contact lens with the iodine disinfectant. To avoid this, when the contact lens is disinfected by using the iodine disinfectant, the iodine contained in the disinfectant needs to be reduced by a suitable reducing agent immediately after the disinfection of the contact lens is completed. According to this arrangement, the disinfectant in which the iodine has been reduced is colorless and transparent, so that the disinfected contact lens is protected from being colored by the iodine.
JP-A-9-111298 discloses a composition for a contact lens, which is a combination of a first agent including an iodine germicide and a protease, and a second agent including a sulfur-containing reducing agent and a foaming agent. The second agent is covered with a coating layer for retarding the emission of the sulfur-containing reducing agent in a manner as described below. The disclosed composition includes a nonionic surface active agent in at least one of the first and second agents. The above-identified publication discloses that a soft contact lens is immersed in a treating solution of the first and second agents, so that the soft contact lens is cleaned and disinfected by the first agent. Thereafter, the coating layer of the second agent is dissolved, whereby the sulfur-containing reducing agent included in the second agent is dissolved in the treating solution. Accordingly, the iodine molecules remaining in the treating solution are reduced by the sulfur-containing reducing agent, so that the contact lens and the solution which have been colored in yellow or amber due to the iodine are made colorless.
The composition disclosed in the above publication includes an excessively large amount of the iodine germicide in an attempt to provide a sufficiently high disinfecting effect, and also includes the sulfur-containing reducing agent to reduce the excessive iodine germicide. The use of the sulfur-containing reducing agent inevitably pushes up the cost of manufacture of the composition, and causes a problem that the sulfur contained in the reducing agent may be released, undesirably precipitating in the treating solution. The inclusion of the excessive amount of the iodine in the treating solution increases the effective or available iodine concentration of the solution. In this case, the treating solution may exhibit a high degree of disinfecting effect. However, the contact lens tends to be damaged due to the excessively high available iodine concentration. Further, iodide ions which have been produced by neutralization of the iodine molecules are oxidized back into the iodine. In this case, the contact lens may be colored by the iodine, and the iodine may give rise to a problem of insufficient safety.